JPS59156724A - Manufacture of joining material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] What is the present invention? Rimetaku□LiluimiP core made of plastic foam and a thermoset plastic reinforced with fibers when bonded to the core (which is flowable before curing)
The present invention relates to a method for manufacturing a composite material having a curable layer consisting of a thermosetting plastic by placing an uncured thermosetting plastic on a plastic foam core and curing the bonded material by heating it to a curing temperature. BACKGROUND OF THE INVENTION Composite materials are used in many industrial fields as light, hard, and highly load-bearing parts, such as in the aircraft and vehicle industry, shipbuilding, shipping containers, and other manufacturing.

According to German Published Patent Application No. 3002584,
A composite material of plastic foam consisting of a core made of plastic foam that expands to its original size while generating foaming pressure when pre-compressed and heated, and a thermosetting coating material is used as an adhesive layer material. It is produced by placing it on a core and heating it in a hollow mold, at which time the core simultaneously generates foaming pressure and the coating layer hardens. - A disadvantage of this method is the necessity of pre-compressing the plastic foam of the core.

The production of a plastic foam composite material I1 having a core made of polymethacrylimide plastic foam comprises:
It is described in German Published Patent Application No. 2822884. According to this, foaming occurs at 170 to 250'C.
A thermosetting plastic having fibers is placed on the core of the plastic foam thus obtained and cured at a humidity of at least 40° C. and below the foam flow rate of the core of the plastic foam used. External compression pressure is used to bond the covering layer to the plastic foam core.

This method is only suitable for the production of composite monthly molds in hollow molds with a constant cavity volume.

This is because, after closing the hollow mold, no further compression pressure can be used.

It is known from DE 2009841 A1 to use molded bodies made of polymethacrylimide plastic foam in a two-step foaming process. In this case, in the first foaming step, a preform is produced without pressure, which is optionally processed to form a blank, which is then transformed in a second step by high heating in a hollow mold consisting of several parts. Expand to final form. At the same time the coverage of the covering layer is not evident with this method.

The object of the present invention is to produce a composite porcelain with a core of polymethacrylimide plastic foam without precompressing the plastic foam and without using external compression pressures. The solution to this problem is to use, as the thermosetting plastic of the coating layer, a thermosetting plastic whose curing temperature is within a range of degrees at which the plastic foam softens and generates at least 1 pearl of foaming pressure. Heating the material to a temperature within the above-mentioned range and maintaining the fluid state of the thermosetting plastic at this humidity at least until the plastic foam develops foaming pressure, causing expansion of the plastic foam surrounding it. It has been found that this is possible by suppressing the foaming pressure with a stable hollow mold.

There are many thermosetting plastics that have varying degrees of hardening properties. These vary depending on the degree of curing temperature or the speed at which the curing takes place in the hot stage. If thermosetting plastics not selected according to the invention are used in the production of the vat layer, composite materials are obtained with insufficient bonding between the plastic foam and the cover layer.

The process often used for producing composite phase IC of plastic foams consists of first preparing a plastic sub-layer with a quantity corresponding to the thickness of the plastic layer to be coated with respect to the form of the material to be produced. It is to manufacture a mind made of -mu.

The core is covered with thermosetting plastic and placed into a hollow mold whose hollow space corresponds exactly to the complex to be manufactured. In general, it is almost impossible to accurately coat all parts of the core of the considered thickness with thermosetting Shirasudek, so
The hollow mold cannot be completely closed immediately after loading the coated core, but a second step must first take place to allow the deposited coating to flow from the surplus zone to the deficit zone. Testing of the finished cured moldings revealed that a sufficiently tight bond between the core and the covering layer only resulted in the above-mentioned excess amount 41. This is due to the compression pressure when closing the hollow mold and dispensing the flowable thermoset.

In contrast, in the first deficit band, insufficient coupling between the mind and the affected layer occurs. Air bubbles and cavities are present between the core and the covering layer and even within the covering layer when the covering layer consists of several layers.

This drawback has made Tl difficult in the case of relatively low cure humidity as well as relatively high cure 77 crystallinity. J? In the first case, hardening takes place in the under-dose zone without compressive pressure for a tight bond between the Plusdec foam and the cooperating layer. In the last case, the core generates a foaming pressure which causes the armored layer to become sufficiently hardened that under the action of the foaming pressure it no longer adapts to the contour of the hollow mold and the armored layer This only occurs at the point where the connection between the core and the core is obstructed by cavities and bubbles.

Therefore, it is critical to the present invention that the curing step occur in synchrony with the generation of foaming pressure.

The many methods according to the invention that exist for this purpose are all based on the fact that the core of the plastic foam generates sufficient foaming pressure when the thermoplastic plastic is flowable. The foaming pressure, in conjunction with the surrounding hollow mold, hardens the cooperating layer, resulting in a tight fit 42 to the core of the plastic sub-mold.

If, for technical reasons dictated by the requirements of the properties of the composite material to be produced, it is necessary to use a certain polymethacrylimide plastic film as the core material, it must first be ensured that this is sufficient. Check the temperature that generates foaming pressure. For the covering layer, it is only possible to use thermosetting plastics which are flowable for at least 2 minutes, preferably at least 10 minutes, at a determined temperature and then harden. Conversely, technical reasons may dictate the specificity of the armored layer (in this case the plastic is fluid for the required time and then hardens).
Check the drawing range. The plastic foam is selected from the available polymethacrylic foams to generate sufficient foaming pressure at this temperature.

The adaptation between the thickness of the coating layer and the use of the core can be facilitated by lowering the temperature range in which the plastic foam develops foaming pressure by introducing plasticizers, especially water. Heating can be facilitated by microwave irradiation if this contains a microwave absorbing additive.

EXAMPLES Polymethacrylimide plastic foams can be manufactured by known methods with various properties, particularly persimmon specific gravity, various compressive strengths, and the like. Manufacture is possible, for example, in British Patent Nos. 1i1 994 725 and 1045 229, and in German Patent Nos.
709'6, German Published Patent Application No. 27.262
No. 59 and No. 2726260. These plastic foams are heated to temperatures above the foaming temperature used for their manufacture.
Generates a foaming pressure of pearl or several bars. Since the plastic foam is manufactured at, for example, 170 to 80°C, it will soften again at this temperature, and a foamed foam will be obtained at 180 to 190°C. On the other hand, if a foaming temperature of 200 DEG C. is used during production, the plastic foam must be heated to 210 DEG -220 DEG C., thereby causing the plastic foam to develop a foaming pressure. However, the temperature at which the foaming pressure occurs can be lowered later by adding suitable plasticizing additives to the plastic foam. Water is particularly suitable. By storing the polymethacrylic imi 15 Shirasudek foam against air with a large IJ vs. humidity 30
Up to % by weight of water is absorbed, which makes it possible to reduce the post-foaming temperature sufficiently to, in extreme cases, the θlj IIr# temperature of water. Other plasticizer additives J&i, l1
l) enoba formamide, dimethylpormamide and acetamide, which are vaporized in the same way
can be diffused into plastic foam by J.

As the temperature and time of heating increase, the foaming pressure increases to about 1
It can be raised at 0 bari.

This is advantageous when producing coated composite materials with complex shapes or thick walls.

Examples of thermosetting plastics include resins that are liquid, boiled or pasty, or solid at room temperature, which initially flow when heated, but then become viscous and gradually harden. Resins which no longer turn into a fluid liquid in less than 2 minutes at a temperature where they are hard and do not melt are unsuitable for the process of the invention. After losing fluidity, the resin does not solidify immediately but first becomes a gel. When using forming force in this state, 4 will be completely cured, and 4 will have strength that cannot be used.
144-1 is generated. It is therefore important that all flow- and molding steps are completed when foaming pressure is applied to the coating layer before the resin changes from a fluid state to a gel state or a hardened state.

Typical thermosetting plastics suitable for the method of the present invention: ami7nolast resin, epoxy resin, polyester resin;
Belongs to the group of phenol@J fat and imido tochi fat.

The resins are on the market, for example, combined with reinforcing fibers as so-called "prepregs". The fibers can be, for example, glass, carbon, rock wool or natural or artificial fibers, free or bound in the resin. It may be in the form of a woven fabric, knitted fabric, or knitted fabric.i) It may be present in the form of a fabric or frith.Generally, a flat molded body having 0.4 to 6 times the weight of fibers is impregnated, and , can be placed on the mind in several layers depending on the case.

The core of the plastic foam is generally completely surrounded by a layer of thermoset plastic, but this is not critical to the invention. Rather, the heart may be uncovered in places. In the same way, separate, optionally non-contacting parts may be included in the molded body and bonded to each other by a layer of thermosetting silica.

A composite made from the core and the material of the coating layer placed on top is
Its final form is obtained upon curing in a hollow mold. It must withstand the foaming pressure without significant deformation. This is because the deformation is not taken into consideration in the final molding. Also in this case, the counterpressure of the mold must be sufficient to ensure the necessary compaction and bonding of the material of the covering layer.

The cavity of the closed hollow mold defines the final form of the composite material. Generally, a hollow mold can be divided into several layers, so the finished molded product can be easily taken out. In the case of simple moldings without cutting gIS, a mold consisting of two mold halves that are tightly connected during the curing process is sufficient. Inserts may be used in the hollow mold, which engage the recesses during curing.

The forming tool is pretreated so that it can be easily separated from the application of the cured coating layer. however,
The hollow mold may be a component of the composite material, in which case it is preferably fixed to the grooves of the storage layer. For example, a circular plastic foam core can be coated with thermosetting plastic, inserted into a tube sleeve, and cured therein. However, the hollow mold included in Composite 41 material does not need to be a rigid body. A sufficiently pressure-resistant textile hose impregnated with thermosetting plastic, for example by the prepreg method, is sufficient. A core made of plastic foam is inserted into the hose and the composite is heated, the foaming pressure being absorbed by the hose.

The composite consisting of a plastic foam core and a thermosetting plastic is heated in a hollow mold at e.g. 180-250°C.
heating to a curing temperature that lies within the range of . It is not necessary to heat the entire core; it is sufficient that a layer with a thickness of 10 to 30 mTn can generate the foaming pressure. This is generally 10
Lasts ~60 minutes. The heating time can be significantly shortened by simultaneously irradiating the bonded material with microwaves having a wavelength of, for example, 2/1501 φHz. Such radiation is hardly absorbed by pure polymethacrylimide. However, if the plastic foam contains radiation-absorbing additives, for example water, it heats up quickly and can reach foaming humidity in seconds or minutes. If thermosetting plastics are also heated by microwave irradiation, other heat sources can be dispensed with altogether. When the thermosetting plastic has finished curing, the deagglomerated material is allowed to cool in the hollow mold, and is removed after cooling to a temperature at which undesired deformation no longer occurs.

Claims (1)

[Scope of Claims] 1 No. 1 A core made of polymethacrylimide plastic foam and a covering layer made of a thermoset plastic (which is flowable before curing) optionally reinforced with fibers if bonded to the core. A method in which a composite material is manufactured by placing an uncured thermoset plastic on a core of plastic foam and heating the composite to a curing temperature to harden it. Using a thermosetting plastic that exists within a temperature range that produces pearls, the composite is heated to a temperature within said range, at which temperature the flow state of the thermosetting plastic becomes less A method for producing a composite material, which continues until the plastic foam generates foaming pressure, and the expansion of the plastic foam is suppressed by a stable hollow mold surrounding the plastic foam and aligned with the foaming pressure. 2. A method according to claim 1, characterized in that the plastic foam contains a plastic additive that lowers the altitude range in which the plastic foam softens and develops foaming pressure. 3. Absorption addition in the microwave range Microwave irradiation is applied during the curing of thermosetting plastics without any additives.
This promotes heating of the plastic foam with humidity that softens the plastic and generates foaming pressure.
A method according to claim 1. 4. Process according to claim 2 or 3, characterized in that the plastic foam contains 0.1 to 30% by weight of water as plasticizing additive and microwave absorbing additive. 5. The method according to any one of claims j to 4, wherein the curing is carried out in a hollow mold consisting of several parts, and the mold is released after the end of curing and after at least a partial cooling of the composite material. . 6. A method according to any one of claims 1 to 4, wherein the curing is carried out in a hollow mold, which mold consolidates with the thermosetting plastic and becomes a component of the composite monthly rate. 7. The method according to claim '6, wherein the hollow mold is made of a porous woven or knitted fabric impregnated with thermosetting plastic.